It is truly amazing stuff. I've fixed a lot of coolers with it, my shoes, a big assed water fountain pump and a garbage disposal. Once it cures it seems to be stuck there forever, tolerates pressure, heat and flexing pretty well, and doesn't leak that I can see. It isn't all that strong, kind of like putty when you pull it out and like a rubber eraser when it cures.
Couple of things;
It does have a shelf life, expect to replace it every year. High heat and humidity seems to break it down faster. It costs like $3 for a gob about the size of a marble.
It comes in little foil packets and if the seal is broken this stuff cures, so a hard container to keep the packets in is a good thing.
I wouldn't even try and patch a boat with it, and probably not a dry bag or a life jacket. Unless I saw no other option. Besides, that's what duct tape is for.
You can mold it and mess with it for about half an hour before it needs to be left alone.
It cures in a few hours, but the package says curing is 24 hours. You been warned.
The shit stinks, even after it cures. Kind of smells like vinegar or musty socks.